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Vacuum tank problems

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Eddie's 25 Franklin is having a vacuum tank problem  It has baffled us for about 2 weeks. Here are some of the things we have checked. We checked for engine vacuum, plenty. We disconnected the fuel line at the Gascolator and blew through it. Clear. We hooked a vacuum pump to the gas line and drew gas through it, by the way, the tank is full. We took the tank apart and checked for pinholes in the inner tank. We have two inner tanks and both are fine.We checked the top section for cracks, none and not warped. There are 2 new springs in the top section and the 2 pins seem to be operating fine.   I had Eddie remove the gas line and check for vacuum at that point, Nothing. When we put the inner and outer tanks back together, we used new gaskets. We had a suggestion to put gasket sealer around the outer edges of the tanks. Did not make a difference. We checked the float (we have two of them too). Both were fine. When we prime the tank, the car will start and run fine until it runs out of gas. We checked the line from tank to carb and the outlet valve at the tank. Everything checks out. It is apparent that the problem is lack of vacuum, but where is the gremlin that is causing the problem? I hate to see Eddie frustrated, he's 26 years old and loves his Franklin and his 26 T runabout. I've got to get this 25 running. Eddie says No electric fuel pump! Dave

Henderson on Sweetser Rd..JPG

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do you have a way to make sure the vent is closing and sealing when the float is low.   Sounds like you have check everything else, if thae vent does not close the vaccum will not pull the gas into the tank.  

Good Luck

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You have to run them with a "rubberize" type or neoprene cork gasket of about 1/32  to 1/16 inch thick - if running a paper gasket you will never get them to work.  Also, I have had solder joints crack. You could have a pickup tube problem in the tank as well.   And, you have to shut them off when not in use.  Also, check for cracks in the die cast housing. = There is an Australian company that makes a nice reproduction top http://www.vintageandclassicreproductions.com or you can keep an eye out via such as this forum, ebay, or www.franklincar.org.  I agree about the vent too.

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Is there a vacuum line from the tank to the vacuum windshield wiper?

My car has a metal line to under the dash, a 4 inch rubber line, then a metal line to the wiper.

Replacing the rubber line fixed my slow wiper problem.

 

I have converted to a 6 volt electric pump next to the tank in the rear, you will also need a fuel flow regulator.

 

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Make sure your gas cap is vented & use gas tank sealer or super glue to seal the underside of the pot metal lid for the vacuum tank.  The pot metal lids can develop porosity that is very hard to detect.

Edited by Mark Shaw (see edit history)

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How many screws are holding the top to the canister?

Without going out the shed now if the inner canister has a very narrow flange on it only ONE gasket made of CORK is used........don't ask me how I found out!

If the canister has a wide flange then two gaskets are used.

Did you verify that both needle seats in the cover are, in fact, working? Or even there?...... :wacko:

 

Maybe this will help >>> http://www.allpar.com/fix/fuel/vacuum-tank-fuel-pump.html

 

Edited by cahartley (see edit history)

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46 minutes ago, cahartley said:

How many screws are holding the top to the canister?

And make sure that the cover's vent hole is aligned with the vent hole in the can--or you will have NO venting.  On most S-W tanks, it is possible to inadvertently block off the vent hole.  Wish they had staggered the screw holes to preclude this.

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I have run several cars with vacuum tanks. Once you get the bugs worked out? They usually work fine are are fairly reliable.

One, that gave me fits for awhile, the car had sat for a few years. The gasoline tank had sat with the cap off for a few of those years, and gotten some leaves and other junk in it. I did a quick clean out, and took the car on a major tour. It started off okay, then developed fuel line plugging issues. We limped along, blew the fuel line out, limped some more, then blew the fuel line out again. All the several times, we checked the float, checked the vacuum tank valves function, always just fine. Got the car going again. Went about ten more miles, and the car did something different. Instead of starving for a plugged fuel line, it got way rich, stumbled, smoked, quit. The float, in about ten miles, had developed several splits from top to bottom, filled with gasoline and sank. I figure that some of the leaves had left an acidic residue which attacked the brass in the float.

I had a short piece of fuel line hose in my tool kit. With a little creativity, rigged it into the vacuum line routed through the firewall to inside the car. Using a bolt as a plug, we manually applied vacuum to the tank when we thought it would need it, then plugged the line to the engine to not overly lean the fuel mixture. Kept on touring.

 

Over the next year, I did quite a bit of work on that car, including replacing the failed float.

 

Now, we get to the part that may apply to your immediate problem.

The next year, we went on a tour again. Symptoms very much like you describe. But not quite like we had the year before. The car had run quite a ways for awhile, then began doing like you describe. A bunch of roadside diagnostics kept saying the fuel line itself was not plugged (I had blown it out quite well). We limped through the tour, and took the car home. With better than roadside lighting and tooling, I found it. A small amount of upholstery cotton, inside the vacuum tank's top piece itself. Probably the remains of a mouse nest that had been inside the gasoline tank, sucked into the fuel line (causing some of the earlier line troubles), had eventually found its way into the input fittings and the valve chamber itself. It partially plugged the fuel path where it was hard to find, and probably also interfered with the valve's action.

 

Check the valve action. As the float goes up and down with fuel level (in the vacuum tank), the two valve stems also switch up and down. Both up, or both down, One of the two stems will open a path, while the other will close a path. One of them also opens and closes the vent path (probably not your trouble). With the tank top off the tank (always be careful handling as the float supports, springs, and valves can be damaged easily). Rig up fittings and tubing or hoses onto both the vacuum line and the fuel input line.The simple thing to do is just blow (exercise your lungs) into one or the other, while carefully moving the float assembly up and down. Switch it many times and get a feel for it. Both lines should have a clean clear switch from clean open to nearly totally shut. The switch should be swift, and decisive. One direction should be open, the other closed. Always, quick, and decisive. It doesn't get much simpler than that.

It would be good to check the vent path also? But the few I have checked seemed a little less decisive with its switching? So, I am a little less sure what to describe about it.

Also, be sure that flapper valve between the upper and lower chambers is smooth and flat, seating really well. They sometimes warp with age, and if they are not nearly perfectly flat and seal really well? They will allow the vacuum in the upper chamber to suck the gasoline back up from the lower chamber rather than pulling gasoline from the gasoline tank. Understand, that simple flapper valve is not expected to seal a hundred percent. If that were necessary, they would have used a different type of valve. They are intended to do a quick dump of the upper chamber if needed, without restricting the slow flow down usually needed. 

 

The entire mechanism is a marvel of engineering. The fact that so many of them are working so well after nearly a hundred years is amazing.

Good luck with it! I hope you find some silly little thing and get it working fine soon. Because they can be frustrating until you evict all those little bugs. (Like a pencil eraser size piece of cotton.)

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My similar problem was traced to a bad flapper valve. The bad one looked exactly like the good one. I have used gas tank sealant inside both the inner and outer tanks to seal small leaks. Sometimes you can place a light bulb inside of the outside tank while in an otherwise dark room and find pin holes and leaks around the seam. Zeke

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I sounds like a valve not sealing properly or the vent hole alignment.  I used a Permatex aviation sealant on the gaskets (nasty brown stuff) that holds up to gasoline.  Getting it apart again in the future will be fun...  The light bulb idea is a good one. 

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Check very carefully the brass valve seats that are in the diecast top. If they have come loose you will get intermittent trouble where the seat will allow air to be sucked between the brass insert and the diecast. We had one give us lots of trouble, it would only drop out of the diecast once in probably every 100 operations. We used loctite bearing lock to fix the problem. A small drop of this stuff on the brass, then pushed back into the diecast, solved the problem and it has operated perfectly the last 10+ years

Viv.

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Olympic, 

 

Lots of great tips and advice given above. Please let us know what happens and what you find out. 

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Thanks to everyone for the suggestions. We still haven't figured out the problem, but close examination of the seats for the 2 valves in the tank top may be the problem. I have another top and I may swap that today. We've made new gaskets too. I'll let every one know what happens. Dave

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Agree with Viv W. I've had the brass seat come loose on a '29 Packard -- it would go great for hours and then suddenly shut down. Had a hard time finding it. Now it would be the first thing I would check.

 

I also had success with smoothing out the flapper valve at bottom with 1,000-grit sandpaper; the valve was slightly warped. Now it seals well.

 

 

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I had a 1928 Erskine with a similar problem, there was an elbow for the fuel line (I think it was the fuel line, but may have been the vacuum line, it was 30+ years ago) on the top of the vacuum tank that had a relatively small orifice (no idea why) which was plugged with a small paint fleck. Once that was cleaned out it functioned fine, but made for a long ride home, draining gas from the gas tank to manually fill the vacuum tank every few miles.

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Stude24, You should have found that fitting with the small orifice in the vacuum line going into the vacuum tank. Its purpose is as a "backfire muffler". In order to work well under most road conditions (High speeds, going slow, or climbing hills, they needed to use a fairly large line (tubing, usually about 1/4 inch). The problem with that large a vacuum line is that IF the engine backfires (for either timing or fuel mixture reasons) back through the intake manifold and carburetor? The sudden burst of pressure can carry up the vacuum line tubing and if left unhindered, can blow the brass seat out of the tank's top. A simple fix as mentioned above. But very annoying if it happens again and again. That seemingly useless odd fitting provides a break in the pressure flow, a virtual "brick wall" when a burst of pressure hits it. Reasonably steady vacuum flows by it almost without even noticing it, but the sudden burst of pressure and direction change trip up on it almost every time.

 

Years ago, I did have a 1925 Studebaker small 6 that had troubles blowing that seat out from time to time. (Very annoying!) I tried a couple top units. Same trouble. I decided to bypass the vacuum line to inside the car, under the cowl, with a shut-off valve in case I needed it. I don't think I ever needed the shut-off valve. Drove the car for a few years with no more trouble. I suspected the detour with several bends and a few changes in internal size helped to further muffle the backfires enough that the problem went away.

The car always ran so nice, I rarely ever heard any misfires. But there must have been a few quiet ones to blow that seat out the way it did.

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Wayne,

 

Thank you for the explanation (and the clarification) about the vacuum line fitting. I always wondered why they would put such a restriction in the fitting. The other thing about it was that it wasn't obvious looking at it from the outside, you had to remove the vacuum line to see the restriction. I suspect there aren't many people around today who have this kind of knowledge. Thanks for sharing.

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The engineering drawings for that fitting (Franklin part # 33111) on my 1926 Franklin Series 11A call for the small hole to be a #56 drill = .0465"

 

Roger

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